The present invention relates to clutch plates, especially to clutch plates of the type which can be put to use in friction clutches of motor vehicles, for example, to transmit torque between the flywheel on the crankshaft of an internal combustion engine and the input shaft of a variable-speed transmission. More particularly, the invention relates to improvements in clutch plates of the type wherein a hub (which can be connected with the input shaft of the transmission) is movable angularly (within limits) relative to the carrier or carriers of one or more friction linings (such friction linings serve to receive torque from the aforementioned flywheel if the clutch plate is used in the friction clutch of a motor vehicle).
In clutch plates wherein the hub is turnable within limits relative to the friction linings, angular movements between the two units of the clutch plate are opposed, at least within a portion of the full range of angular movability of the two units with reference to one another, by one or more energy storing devices in the form of coil springs which are installed in registering windows of a flange on the hub and of the carrier or carriers of the friction linings. It is further known to provide friction generating elements which are installed between the two units of the clutch plate to oppose angular movements of the hub relative to the friction linings and/or vice versa. The friction generating elements can oppose each and every angular movement of the two units relative to each other or only certain stages of such angular movement.
German Offenlegungsschrift No. 2,814,059 discloses a bearing ring which is interposed between the hub and the carriers of friction linings in a clutch plate and has a substantially L-shaped cross-sectional outline i.e., the bearing ring includes a radially extending collar and an axially extending sleeve. The bearing ring is non-rotatably affixed to the carriers of friction linings and its sleeve-like portion surrounds the hub to thus ensure that the carriers are centered on the hub. The radially extending collar of the bearing ring is biased against the radially outwardly extending flange of the hub. The biasing action is performed by a spring which reacts against one of the two coaxial spaced-apart disc-shaped carriers of the friction linings. The flange is disposed between the two discs and the spring reacts against that side of the flange which is not contacted by the aforementioned collar of the bearing ring. In this way, the other disc, which is connected to the bearing ring, is urged in a direction to maintain the collar in frictional engagement with the respective side of the flange.
As a rule, the sleeve of the bearing ring surrounds the hub with at least some radial clearance. Such clearance is established as a result of manufacturing tolerances as well as to facilitate assembly of the clutch plate. An undesirable phenomenon which is attributable to the provision of this clearance is that it limits the extent to which the clutch plate can be balanced, i.e., a friction clutch which embodies the clutch plate is likely to create problems (particularly noise and extensive wear) due to the absence of accurate centering of the carriers of friction linings relative to the hub. A problem which is most likely to arise is excessive vibration of the clutch plate which, in turn, brings about excessive wear upon the parts which cooperate with the clutch plate as well as pronounced reduction of comfort to the occupant or occupants of the motor vehicle if the clutch plate forms part of a friction clutch for motor vehicles. Moreover, vibrations cause an increase of the radial clearance between the sleeve of the aforementioned bearing ring and the hub to thus further increase the unbalance to an extent which becomes intolerable and renders it necessary to replace the clutch plate or the entire friction clutch. The wear upon the sleeve of the bearing ring and/or upon the hub of the clutch plate is also attributable to the action of radial forces which develop when the clutch plate is in use; such forces contribute to unbalance with the aforediscussed undesirable consequences.